Presses

ABSTRACT

A machine for compacting metal powder comprises a static frame, a die having a bore, a lower punch defining a receiving die cavity in the bore, an upper punch, an upper punch downwardly movable to enter the die cavity, and a reaction frame to which the lower punch is fixed slidably mounted on the static frame, the reaction frame and the lower punch being moved upwardly by a reaction force generated when the upper punch is moved downwardly. The die is moved upwardly after the die cavity has been filled with powder a distance at least equal to the upward movement of the lower punch completed before the upper punch enters the die cavity, and the die is moved downwardly after the upper punch has entered the die cavity.

United States Patent [15] 3,659,985 Marshall et al. 1 May 2, 1972 [54] PRESSES 3,414,940 12/1968 Vinson ..18/16.$ x 72 Inventors: Alec Frank Marshall, Solihull; Hugh Gor- X do Taylor Birmingham both of England 3,115,676 12/1963 Quartullo ..18/D1G. 28 3,158,048 11/1964 Bollar 18/DlG. 28 [73] Assignee: The Birmingham Small Arms Company 3,571,854 3/1971 Lundstrom ..18/16.5

Limited, Birmingham, England 0 E] N E P I o F R G PAT NTSORAP LC Tl NS [22] Filed: Dec. 9, 1969 A 9 ..1 pp NO: ,4 5,573 1 62 Japan 8/16 5 Primary Examiner-J. Spencer Overholser [30] Foreign Application Priority Data Assistant Examiner-Donald M. Gurley Dec. 13, 1968 Great Britain ..O59,302/68 Mar. 15, 1969 Great Britain ..l3,723/69 ABSTRACT Cl 1 /264, 72/45 A machine for compacting metal powder comprises a static 425/352 frame, a die having a bore, a lower punch defining a receiving [51] hit-Cl ..B30b 11/02 di c vity in the bore. an upper punch, an upper punch Field of Search 18/165, 16-7, 1316- 16 R; downwardly movable to enter the die cavity, and a reaction 25/90 91; 72/453 frame to which the lower punch is fixed slidably mounted on the static frame, the reaction frame and the lower punch being [56] References cited moved upwardly by a reaction force generated when the UNITED ST T PA ENT upper punch is moved downwardly, The die is moved up- A Es T S wardly after the die cavity has been filled with powder a 2,023,021 1/1936 PPY distance at least equal to the upward movement of the lower ,491 l/1944 Cutler 1 punch completed before the upper punch enters the die cavi- 2,796,633 6/1957 Carlson et al... 1 8/16- ty, and the die is moved downwardly after the upper punch has 2,825,092 3/1958 Hatch et al. ...18/l6.7 entered h di it 3,132,379 5/1964 Crane ...l8/16.5 3,154,812 ll/1964 l-laller ..25/91 X 5 Claims, 2 Drawing Figures 7 a a 41$ 70? Z A, A

2 1: t \9 (P 4 1'7 23 zzt li PATENTEDHAY 2 m2 SHEET 10F 2 w U0 w M b@//////// w w A r 4 m H W 4 f w 2 V///\\ m1 nil r: ALEC FRANK MARSHALL and HUGH GORDON TAYIOR Attorne PATENTEDMAY 2 1912 3, 6 59 98 5 SHEET 2 BF 2 Inventors ALEC FRANK MARSHALL and HUGH GORDON TAYLOR Inventors PRESSES This invention relates to the production of shaped components of metal and other powders (hereinafter referred to generically as metal powders") which are subsequently sintered to form finished or semi-finished components. The methods of producing these, involving presses, usually hydraulie, in which the powder is compacted in a die, are well known. The increasing demand for larger components and higher densities has led to the experimental use of high energy rate forging presses adapted for compacting metal powders. These presses, which usually have rarn velocities up to 60 feet per second, have the advantage of higher ratio of energy to press weight than conventional presses.

With conventional (low speed) compacting of powders, the effect of friction between powder and diewall is minimized either by moving upper and lower punches towards each other in a fixed die, or by moving the die downwards at approximately half the speed of the upper punch, towards a fixed lower punch.

An accepted feature of high energy rate compacting machines is the use of a floating or reaction frame to which the high energy rate cylinder is attached. This frame is provided with vertical movement so that when the ram is fired downwards, the upward reaction energy lifts the frame upwards. The relative velocity of the reaction frame, ignoring gravity, is determined by the momentum equation, which may be written e e) (WI/W1) where R Ram velocity F Reaction frame velocity W,= Weight of reaction frame and W,= Weight of ram and results in a reaction frame velocity typically between onetenth and one-twentieth of the relative ram velocity.

The dieset is normally attached to the reaction frame in such a manner that both die and lower punch move upwards at equal velocity. With this arrangement the optimum conditions for reduction of friction between powder and die cannot be obtained.

Suspension of the die upon a separate floating mechanism within the reaction frame would ideally restore the optimum conditions, but in practice is very difficult, due to the nature of the compacting cycle. The powder to be compacted normally fills the aperture between the face of the lower punch and the upper surface of the die and for this reason no downward die motion is permissible until the upper punch has completed its free downward movement and entered the die. The reaction frame is forced upwards with an acceleration of several 8 at the moment the upper punch begins its downward movement and the dieplate floating mechanism would therefore have to resist the acceleration forces without downwards movement relative to the reaction frame. Under these conditions the floating mechanism would be so stifi' as to be entirely ineffective.

Another factor affecting this problem is the tendency for the surface layers of powder to be seriously disturbed by the pocket of air trapped under the rapidly moving upper punch.

The present invention provides the underfill conditions necessary to prevent or minimize disturbance of the powder surface and also provides powder/die friction conditions which approach the optimum conventional conditions.

According to a feature of this invention a high energy rate press for producing compacts of metal powders of the kind in which an upper punch is affixed to the ram of the press and a lower punch is affixed to a reaction frame, said ram descending and reaction frame ascending relative to the static frame of the press during the compaction stroke of the press, has a die defining the periphery of the compact to be produced movable relative to the reaction frame. Upward movement of the reaction frame and the lower punch is effected by a reaction force created on the reaction frame during the compaction stroke.

According to a further feature of this invention a press of the kind referred to is constructed so that the lower punch moves upwardly relative to the die.

According to a still further feature of this invention a press of the kind referred to is constructed so that ejection of the powder compact is effected by means of an ejector mechanism attached to the static frame which mechanism lifts the reaction frame and lower punch upwards while the die is prevented from moving.

An example of carrying out the invention is shown in the accompanying drawings in which:

FIG. 1 shows in diagrammatic form the arrangement of a high energy rate press according to the invention; and

FIG. 2 shows diagrammatically the movements of the tool items during the operations of a complete cycle.

Referring to HO. 1 the ram 1 to which the upper punch 2 is attached, is adapted to move within the cylinder 3 which is attached to the reaction frame 4. The lower end of the reaction frame terminates in the plate 5. The vertical motion of the reaction frame is guided within the static frame 6 by rollers 7 or by other suitable means. The static frame 6 extends downwards and terminates in the plate 8. The surfaces 9 on the static frame 6 support plate 5 of the reaction frame 4, when the machine is at rest.

The lower flange plate 10 supports the lower punch 11 and is rigidly attached to the reaction frame 4. The dieplate 12 which carries the die is guided by column 13 passing through the lower punch plate 10 and attached to the yoke 14 which has a large 25 adapted to be engaged by stop means, as will be hereinafter described, to limit the movement of the die.

The complete dieplate unit 12, 13, 14 assumes four different levels in the vertical plane during the machine cycle, and is shown in the highest (underfill) position, in which the die surface is raised above the powder surface. This position is obtained by moving the dieplate unit upwards until the flange 25 abuts the head of column 15 which extends therethrough. The lower end of column 15 is rigidly attached to the base 8 of the static frame 6.

The powder filling position is controlled by the adjustable and removable stop 16 which contacts the underside of flange 25. The piston 17 tenninates the column 24 depending from flange 25 and is disposed within cylinder 18 attached to the underside of base plate 5 of reaction frame 4. Movement of piston 17 within cylinder 18 moves dieplate 12 between the underfill and powder filling positions.

A further adjustable and removable stop 19 controls the minimum dimension between the face of lower punch 11 and the upper surface of die 12 at the moment of final compression. Stops l6 and 19 both rest upon the upper surface of plate 5 and are removable horizontally by means of linear actuators 20 and 21.

Vertical movement of reaction frame 4, is controlled by dashpot 22 which is arranged to provide minimum resistance during the upward movement, and greater resistance during the downward return movement.

Ejection of the powder compact after compacting is effected by means of linear actuator 23 which is attached to the baseplate 8 of static frame 6, and moves lower punch 11 by lifting reaction frame 4. 1 I

The operating cycle, which is illustrated in FIG. 2, begins with the machine in the ejection position, and the previously completed compact resting on the lower punch, level with the die surface.

OPERATION l The powder filling shoe 26 moves over the die, away the previous compact.

OPERATION 2 pushing dieplate being held in its uppermost position in which the flange 25 abuts the head of column 15.

OPERATION 3 OPERATION 4 The powder filling shoe is withdrawn, scraping off surplus powder level with the die surface.

OPERATION 5 The die is returned to the underfill position in which the flange 25 abuts the head of column 15 leaving the surface of the powder typically 0.5 inches below the die surface. This dimension should be approximately equal to the upward movement of the lower punch and reaction frame during the downwards free movement of the upper punch (with inches free movement of the upper punch and relative velocity of the lower punch one-twentieth that of the upper punch, the movement of the lower punch would be 10/20 0.5 inches). Simultaneously the fillheight step 16 is moved out of engagement and replaced by the punch/die stop 19.

OPERATION 6a.

The ram 1 and consequently the upper punch 2 are fired downwards, and the reaction force urges the reaction frame 4 and lower punch upwards. While the upper punch completes its maximum free travel of 10 inches the lower punch moves upwards 0.5 inches. The powder above the lower punch is however, further densified by the sudden upward movement of the lower punch so that its upper surface still lies somewhat below the die surface when the upper punch enters the die.

OPERATION 6b The powder is now trapped in the die between the punches and is compacted as the opposing punch movements are completed. The relative movements of the punches as they decelerate will still be in the ration of 20 l. The die has not moved during the punch movement of Operation 60, being maintained in its highest (underfill) position by the head of column and the air cylinder 18. As the upper punch has the greatest movement during this operation, the greatest friction effect will be downward and will tend to overcome the inertia of the die assembly and move it downwards. Simultaneously with the firing of the upper punch, the fluid pressure in cylinder 18 will be reversed, but the time lag caused by buildup of pressure in the fluid cylinder will delay die movement downward until the upper punch free movement is completed. By careful timing of the pressure reversal, the die plate can be urged downward by the reverse pressure in the air cylinder 18 as compaction begins, and thus reduce the inertia forces to a minimum. The die stop 19 acts to limit the maximum downward movement of the die relative to the lower punch. Means other than fluid cylinders may be employed in the actuation of the above.

OPERATION 6c Immediately after compaction is completed, the reaction frame 4 rebounds downwards and comes to rest upon the surfaces 9. While the acceleration upwards is relatively high, the rebound, damped by the dashpot 22, can be controlled to any convenient rate. As the die plate is now being urged downwards, in this example by fluid cylinder 18, the compact is held firmly against the face of the lower punch during the rebound. The upper punch 2 and ram 1 are also resting upon the upper face of the compact, which is therefore completely contained during the rebound.

OPERATION 7 The upper punch 2 and ram 1 are withdrawn into the position and the die stop 19 is disengaged.

OPERATION 8a The ejection ram 23 now lifts the reaction frame 4 and lower punch 11 upwards and simultaneously the pressure in cylinder 18 is reversed and urges the die plate unit upwards.

OPERATION 8b The die movement stops when flange 25 comes into contact with the head of column 15. The ejection ram 23 continues to move reaction frame 4 and lower punch 11 upwards, and the compact is ejected from the die.

The advantages arising from the invention are:

l. The several powder movements within the die during operations 2, 3, 5 and 6a ensure that all or nearly all air pockets in the powder due to bridging of particles are removed and the loose powder approaches optimum density prior to the actual compaction.

2. The double compaction effect obtained by the opposed motion of both upper and lower punches within the die reduces die friction during compacting and improves density distribution within the compact.

3. Die movement during compacting further improves the powder/die friction conditions and in conjuncn'on with the ef feet in paragraph 2 above provides optimum or near optimum compacting conditions.

4. The location of the powder surface below the die surface at the point of upper punch entry reduces disturbance of the surface layers of powder by the air cushion under the upper punch.

5. Location of the ejector rams (when using a hydraulic form of linear actuator) on the static frame, instead of on the reaction frame as in earlier designs, greatly simplifies the high pressure hydraulic system, obviating the necessity for flexible connections and avoiding the inertia and pressure surge problems which were inherent in earlier designs.

What we claim is:

l. A machine for compacting metal powder comprising a static frame, a die having a bore therethrough, a lower punch extending into said bore which thereby forms a powder receiving die cavity in the bore, an upper punch, a reaction frame to which the lower punch is fixed slidably mounted in the static frame, firing means for moving said upper punch downwardly to enter the die cavity to compact the powder therein and for creating a reaction force on said reaction frame, said reaction frame and the lower punch affixed thereto being moved upwardly by said reaction force generated when the upper punch is moved downwardly in a powder compaction stroke, means to move the die upwardly after the die cavity has been filled with powder a distance at least equal to the upward movement of the lower punch completed before the upper punch enters the die cavity, and means to move the die downwardly a predetermined distance after the upper punch has entered the die cavity.

2. A machine for compacting metal powders according to claim 1 wherein a reversible fluid pressure operated linear actuator carried by the reaction frame is the means for moving the die upwardly and the means for moving the die downwardly.

3. A machine for compacting metal powder according to claim 1 having means to hold the die stationary whilst the upper punch completes its downward movement before entering the die.

4. A machine for compacting metal powder as defined in claim 1, comprising a first stop means on said reaction frame movable into the path of descent of the die for determining the powder filling position of said die relative to the lower punch.

firing 5. A machine for compacting metal powder as defined in claim 4, comprising a second stop means on said reaction frame movable into the path of descent of said die for determining the distance between the lower punch and the upper surface of the die at the moment of final compaction. 5

1F i I l 

1. A machine for compacting metal powder comprising a static frame, a die having a bore therethrough, a lower punch extending into said bore which thereby forms a powder receiving die cavity in the bore, an upper punch, a reaction frame to which the lower punch is fixed slidably mounted in the static frame, firing means for moving said upper punch downwardly to enter the die cavity to compact the powder therein and for creating a reaction force on said reaction frame, said reaction frame and the lower punch affixed thereto being moved upwardly by said reaction force generated when the upper punch is moved downwardly in a powder compaction stroke, means to move the die upwardly after the die cavity has been filled with powder a distance at least equal to the upward movement of the lower punch completed before the upper punch enters the die cavity, and means to move the die downwardly a predetermined distance after the upper punch has entered the die cavity.
 2. A machine for compacting metal powders according to claim 1 wherein a reversible fluid pressure operated linear actuator carried by the reaction frame is the means for moving the die upwardly and the means for moving the die downwardly.
 3. A machine for compacting metal powder according to claim 1 having means to hold the die stationary whilst the upper punch completes its downward movement before entering the die.
 4. A machine for compacting metal powder as defined in claim 1, comprising a first stop means on said reaction frame movable into the path of descent of the die for determining the powder filling position of said die relative to the lower punch.
 5. A machine for compacting metal powder as defined in claim 4, comprising a second stop means on said reaction frame movable into the path of descent of said die for determining the distance between the lower punch and the upper surface of the die at the moment of final compaction. 